1. Field of the Invention.
This invention relates to a method and apparatus for drilling holes and, more particularly, to a method and apparatus for easily adjusting and setting a depth sensing and signaling mechanism for use when drilling holes having substantially similar depths.
2. Discussion.
Drill presses are used in a wide variety of applications to form or create holes or openings in an object. For example, a rail-type drill press is adapted to form holes in the ends of railway tracks in order to allow fish plate bolts or other types of fasteners to be put through the drilled holes, thereby securing the railway ends together. Additionally, for example, drill motors mounted on a slide mechanism are used to form precisely aligned holes in many other types of objects as well.
In order to reduce the operator effort and to minimize the drilling time required, drill presses, including rail type drill presses, have been equipped with power feed devices which incorporate automatic stops. Many of these drill presses have adequately formed holes, but have not provided an easy method for adjusting the stop when the work-piece, the tool bit and the adjustment mechanism are not readily visible to the operator.
For example, prior depth indicating or stop mechanisms, such as disclosed in U.S. Pat. No. 3,724,964 and U.S. Pat. No. 4,909,683, require that the operator measure the depth required by some means and then transfer the required measurement to a setting of the depth stop in relation to a scale mounted in conjunction with the depth stop mechanism. This requires that the operator be able to clearly see the work area and the adjustment mechanism, or rely on trial and error methods which would be time consuming and likely result in defective holes.
This is a particular problem with rail-type drill presses and magnetic base drill presses. Rail-type drill presses are clamped to a rail of a railroad track and the clamping device as well as the drill press' proximity to the ground make adjustment very difficult. Magnetic base drill presses are commonly used to drill holes in metal, such as for example in metal beams in bridges or high rise buildings, etc. These drill presses include a base having an electro-magnet which is magnetically adhered to the metal beam and then the drill motor is moved toward the beam to drill a hole. Because of the versatility of these magnetic base drill presses, they can be mounted vertically, overhead, etc. making it difficult to adjust the automatic stop.